Is a Bug.

Change this file:

addons/web/static/js/formats.js

Find this line in function instance.web.parse_value:

  case 'float':          
     tmp = Number(value); 
     if (!isNaN(tmp))
        return tmp; 

and change for this (Coment whit //)

 case 'float':          
     //tmp = Number(value); 
     //if (!isNaN(tmp))
        //return tmp; 

is working for us

There are a few ways this could be done. One would be to override a lot of functions to have this kind of effet, another could be to define the currency symbol as k€ and then boost the precision by 3 digits.